Edit: This story was awarded 1st place in the “Short Form” category at the 2016 North American Guild of Beer Writers (NAGBW) awards.

From BeerAdvocate Magazine #103:

No one raises their eyebrows when black currants are used in a beer these days, but yogurt? To create the desired tartness and acidity in The Commons Brewery’s Biere Royale—a riff on the cassis-based Kir Royale cocktail—head brewer Sean Burke pitched tubs of the stuff. Specifically Nancy’s brand Greek yogurt. Burke is from Eugene, Ore., not far from the creamery’s location. Plus, it was in his fridge. Remarkably, the creation of that beer for the 2013 Portland Fruit Beer Festival is one the first uses of Lactobacillus found in unpasteurized yogurt to acidify beer. Instead of extensive aging in barrels inoculated with acid-producing bacteria, Burke went with a probiotic-rich dairy product.

“We knew we wanted to have a high amount of acidity,” said Burke at the time. “We took Nancy’s Greek yogurt and created a starter and soured in the kettle. Nancy’s has multiple strains of Lactobacillus… We mashed into the mash tun, lautered into the kettle, then soured the collected wort.”